implement nullability check for Postgres as a query on pg_attribute
implement type name fetching for Postgres as part of `describe()`
add nullability for describe() to MySQL
improve errors with unknown result column type IDs in `query!()`
run cargo fmt and fix warnings
improve error when feature gates for chrono/uuid types is not turned on
workflows/rust: add step to UI-test missing optional features
improve error for unsupported/feature-gated input parameter types
fix `PgConnection::get_type_names()` for empty type IDs list
fix `tests::mysql::test_describe()` on MariaDB 10.4
copy-edit unsupported/feature-gated type errors in `query!()`
Postgres: fix SQL type of string array
closes#107closes#17
Co-Authored-By: Anthony Dodd <Dodd.AnthonyJosiah@gmail.com>
* fix `Pool` to reduce possibility of "leaking" connections
now uses RAII guards to control `SharedPool::size`
* add smoke test for `Pool` to both Postgres and MySQL tests
add `Pool::is_closed()`
* fix documentation re: pool
* refactor pool implementation to not use futures oneshot channels
https://github.com/launchbadge/sqlx/pull/84#issuecomment-580476223
* run cargo fmt
* Pool: remove superfluous guard struct, document some internal methods
